How much oil do you get from an extraction ?

That completely depends on the material you put in.
Here is a few examples :

40 grams low potency industrial hemp containing approx. 1,5% cannabinoids equals a theoretical maximum yield of 450 mg cannabinoids.
The actual yield from an extraction of industrial hemp on Merlin400 is typically 1.000 mg extract, corresponding to a 40-50% cannabinoid content in the extract.

30 grams high potency cannabis containing approx. 8% cannabinoids equals a theoretical maximum yield of 2400 mg cannabinoids.
The actual yield from an extraction of high potency cannabis on Merlin400 is typically 2.800 mg extract, corresponding to a 65-75% cannabinoid content in the extract.